Synchronized airplane-gun-control system



F. WENNER AND F. J. MARTEL.

smcnnomzsn AIRPLANE GUN CONTROL "SYSTEM.

APPLICATION FILED AUG-26, I919.

Patented June 8, 1920.

4 SHEETSSHEET 2.

REEL Esq! awvewtozi F. WENNER AND F. J. MABTEL.

SYNCHRONIZED AIRPLANE GUN CONTROL SYSTEM. APPLICATION FILED Amaze. 1919.

1,342,729. PatentbdJune 8,1920.

4 SHEETSSHEET 3- F. WENNER AND F. J. MARTEL.

SYNCHRONIZED AIRPLANE GUN CONTROL SYSTEM.

APPLlCATl0N FILED Aus.2e, 1919.

1,342,729 Patented June 8, 1920.

4 SHEETSSHEET 4.

anventow:

.FRANK WENNER, OF WASHINGTON, DISTRICT OF COLUMBIA, AND FRED J. IVIAR'IEL,

OF HANOVER, NEW HAMPSHIRE.

SYNCHRONIZED AIRPLANE-GUN-CONTROL SYSTEM.

Specification of Letters Patent.

Application filed. August 26, 1919.

Patented June 8, 1920.

Serial No. 320,014.

(FILED UNDER THE ACT OF- MARCH 3, 1883, 22 STAT; In, 625.)

To all whom it may concern:

Be it known that we, F BANK WENNER and F RED'J MARTEL, citizens of the United States, and residents, respectively, of l/Vashington, D. 0., and Hanover, New Hampshire, have invented an Improvement in Synchronized Airplane-Gun-Gontrol Systerns, of which the following is a specifica- I used by the Government, or any of its officers or employees in prosecution of work for the Government, or by any other person in the United States, without payment of any royalty thereon. h

This invention deals with a synchronizing gear or gun control system for machine guns on airplanes which will permit of the gun being fired between the blades oftthe rotating propeller at any and all permissible speeds of the latter.

To this end' an object of the invention is the provision of an electrical system in which the energy for accelerating the mov-. ing parts of the control system is furnished by the same source as that which ejects the expended cartridge and restores the gun to firing condition, rather than by any type of electrical motor, which would depend upon electrical energy for,accelerating the moving'parts of the control system.

Another object of the invention is the provision of a system of gun control in which the over-all time lag of the various parts, which must act successively between the beginning of the actuation of the control mechanism, and the passage of the projectile through the plane of the propeller is so of stray shots, that is, shots fired when the propeller is not in firing position.

The invention also provides means whereby stray or accidental shots are prevented 1n casethe control system is put out of actron bythe fire from the gun of a hostile machine or other cause.

' A study of the problem of providing a gun control system whereby the machine gun of an airplane can-be fired through the propeller of the same with the propeller rotating at any permissible speed, shows that in many ways an electrical system is most desirable due to its flexibility and ease in making the various parts mechanically safe.

A further consideration, however, of the problem, shows'that if an electrical system 15 used, it is preferable that the energy for accelerating the moving parts of the-control system, such as the sear and trigger motor, etc., be furnished by the same source as that which ejects the expended cartridge, cooks the firing mechanism, and inserts a fresh cartridge, etc., rather than have the energy provided by any type of electric motor, because, if the moving parts are to be operated by an electromagnet or the more usual type of electric motor, the current density in the winding would necessarily be very high, in order to get an action in a reasonably short time.

Therefore, as before stated, this invention provides a utilization of some part of the gun which'moves relative to other parts as the gun reloads, to set the actuating lever or sear trigger. The sear trigger is held in the set or cocked position by an electromagnet that is normally energized and which is denergized, releasing the sear trigger, when it is desired that the gun fire.

\Vith most synchronizing systems the adjustments are made so that the gun fires only a safe distance back of the propeller blades with the propeller at rest, or turning at a fairly low speed, and the gun fires farther and farther back of the blades as the speeds increase.

Vith a propeller speed of 1800 R. P. M. the blades rotate through an angle of about 11 in 1/ 1000 second, and with a two bladed propeller the safety zone between blades may be considered to be about an arc of 145. Consequently if the gun is to be fired at any speed from 0 to 1800 R. I. M. it is necessary either to advance the phase of the control mechanism, as the speed advances, or to make the over-all time lag so small that this change of phase is not necessary. Experience has shown that any special apparatus to change the phase as the speed changes is usually very cumbersome and therefore to be avoided if possible.

Experiments have demonstrated that with a two bladed propeller the over-all time lag will be sufficiently short. to make allowance for change in phase unnecessary, if reduced below .013 seconds. The over-all time lag depends upon the time lag of the separate parts which must act successively between the beginning of the actuation of the control mechanism and the passage of the projectile through the plane of the propeller. This includes the time required to close the switch or switches in the circuit connected directly or indirectly to the propeller or the crank shaft, the time required to reduce the current in the windings of the holding magnet of the trigger motor (the apparatus which actuates the trigger or sear and releases the firing pin of the gun), the operation of the trigger motor and sear, the operation of the firing mechanism or firing pin of the gun, the explosion of the charge and the passage of the projectile to the plane of the propeller. The latter depends upon the ammunition and position of the gun on the plane. With the regular ammunition and the gun at the usual distance of from four to six feet. from the propeller it amounts to about .0025 second. It can not be made much less than this since the position of the gun is more or less fixed by the type of airplane upon which it is mounted, and the use of ammunition, which is much quicker acting, is impractical. Experiments have shown that the time required for the operation of the firing pin of an aircraft gun cannot conveniently be made less than .002 second. (onsequently, the permissible time lag in the control system itself cannot be over .009 seconds, if it is to operate from 0 to 1800 R. P. M., (which seems to be as high as there is any need for) in order to permit the use of an electrical type of gun control as herein described.

In the accompanying drawings, Figure 1 illustrates a diagrammatic view of an electrical system as applied to a machine gun 1nwhich the means for de'elnergizing a holding magnet of the control system comprises a primary and a secondary circuit in inductive relation with each other and with control switches located in the secondary circuit;

Fig. 2 illustrates a diagrammatic view of a modification of the control system in which spring .25. 7

force on the sear trigger in excess of the the holding magnet and a series of control switches are in a single circuit;

Fig. 3 illustrates another modification somewhat similar to the system shown .in Fig. 2 but-with the additional device for controlling the action of the circuit breaking mechanism or commutator for the purpose of eliminating stray shots;

Fig. 4 is a side view of the control mechanism and casingtherefor, as applied to the side of the machine gun;

Fi 5 is a cross section taken on line 5-5 of Flg. 4:. showing the holding magnet and associated parts of the machine gun and the gun-switch Fig. 6 is a detailed view of the inner face of the control mechanism casing, showing the location of the gun-switch and armature extending therethrough;

Fig. 7 is a detailed View of the gunswitch;

Fig. 8 is a detailed view of the actuating mechanism of the machine gun showing the gun switch contact in an engaged position therewith Fig. 9 is a detailed view of the armature;

Fig. 10 is a detailed view showing the engaging mechanism of the sear trigger and sear in safe or inoperative relation;

Fig. 11 is a fragmentary side view of th sear trigger and its relation with the sear and breech bolt;

Fig. 12 is a simplified diagram of the electrical system shown in Fig. 1;

Fig. 13 isasimplified di gram of the elec trical system shown in Fig. 2;

Fig. 14 is a simplified diagram of the electrical system shown in Fig. 3.

In order to clearly show the relation of the electrical system and the mechanical parts of the control system, the essential elements of the control system are diagrammatically illustrated in Fig. 1, and the conventional diagram of the electrical system appears in Fig. 12. In this arrangement, the primary circuit comprises a source of E. M. F. 19 connected with one winding 20 of an induction coil 21. The other end of the winding 20 is connected in series through the coil of the holding magnet 22 of the trigger motor to the source 19. The trigger motor, in addition to theholding magnet mentioned, comprises a scar trigger 23 (shown diagrammatically in Fig. 1 and in detail in Figs. 4, 5 and 9) integral with the armature 24 of the magnet, and a trigger The holding magnet exerts a force exerted on the sear trigger by the sear trigger spring 25, when the said sear trigger is cocked and the current in the circuit has its normal value.

The secondary circuit comprises a secondary winding 26 of the induction coil 21' which is connected at one end through the contact ofa rotary interrupter or commutator 27 to a grounded side of the source 19; while the other end of the induction coil winding 26 is connected to the ungrounded side of the source 19 through two switches 28 and 29 in series, and two or more volition switches 30, 30 in parallel. One switch 28 in the secondary circuit is a volition contact mechanism, that is, either a hand trigger or if desired a mouth switch fully under the control and at the will of the operator at the gun. The second switch 29 is a safety switch operated by some part on the mechanism of the gun, and is closed only when the gun is in firing position.

The additional control switches 30, 30 may be any form of volition switches, and may be provided in case it is desired to put the control of the gun under more than one operator, as for instance, when it is desired that either the pilot or the observer may control the gun by operating one of the switches 30, 30, and cause the gun to fire at the instant that the propeller reaches a firing position.

The rotary interrupter or commutator 27 is the control or timing contact mechanism connected directly or indirectly to the propeller of the aeroplane or the crank shaft of the engine. The circuit controlled by the timing mechanism shown in Fig. 1 is closed only when the propeller is in the firing position.

The scar trigger 23 is cocked by the reloading of the gun, and held in such position by the holding magnet until the current through the winding is reduced below a certain value when the force exerted by the sear trigger spring overcomes the magnetic pull, forcing the sear trigger against the sear 31 and releasing the firing pin 32, or other actuating mechanism adapted to fire the gun.

The condenser 33 and the non-inductive resistance 34, in parallel with the winding of the holding magnet, are for the purpose of preventing sparking at the contacts, and to permit the current in the winding of the holding magnet to decrease on closing the secondary circuit and build up on opening the same at the desired rate.

The induction coil 21 is for the purpose'of suddenly introducing, inductively, into the primary or main circuit a rather high voltage in opposition to that normally in the circuit, when the propeller blades reach the firing position, and the'secondary circuit is closed, and of suddenly introducing a rather high voltage in the same direction as that in the circuit, when the blades pass out of the firing position and the secondary circuit is opened. To this end, it is preferable to provide the primary winding with a greater number of turns than the secondary winding, in order to increase the amount of E.

construction of the trigger motor, including the holding magnet, armature, gun switch and associated parts of a machine gun, reference being had to Figs.'4 to 11, inclusive. The details herein illustrated show an embodiment of this invention, which is attached to an approved type of machine gun, but it will be readily understood that this invention may also be applied to many other types of machine guns, or designed and incorporated within the body of a gun mechanism without departing from the spirit of the invention.

The trigger motor is inclosed in a housing 36, suitably mounted with reference to the gun so that the sear trigger 23 extends into the gun casing 37 in order to engage the sear 31, (see Fig. 5). The sear trigger thus replaces the usual hand trigger.

The sear trigger 23 is preferably made integral with the armature 24 of the holding magnet 22, forming an arm which is pivotally mounted so that the holding magnet is adapted to hold the sear trigger out of engagement with the sear by reason of magnetic attraction on the armature. The holding magnet 22 is of the usual type of electromagnet, including a pair of windings 38, 38, and horizontally disposed poles, 39,39, with their ends spaced apart to form an air-gap adapted to be closed by the armature 24. A compression spring 25 is mounted on a retaining post 40 seated on the lower wall of the housing 36, said retaining post having an extensible member 41 engaging with the extreme end of the armature 24. The spring 25 is placed under .constant compression thereby storing sufficient energy in the spring to release the sear, at the instant the armature is released by the deenergizing of the holding magnet.

In the type of automatic rifle illustrated, the sear trigger 23 is cooked, z'.-e., the armature 24 is moved into closed contact across the poles 39, 39 of the holding magnet, by.

' means of a cam surface 42 on the bolt 43 of the gun (see Figs. 8 and 11), in the following manner: When the gun is fired, the bolt 43 and. sear 31 are thrown backward so that the sear trigger 23 engages with the cam 42, and is forced upwardly thereby. The sear trigger is maintained in raised position during the backward and forward movement of said bolt while the holding magnet is becoming reenergized sufficiently to retain the sear trigger in raised posltion ready to .operate the sear after the bolt and sear resume their firing position.' In the type of gun mechanism to which the inven- "tion is herein applied, the bolt is so constructed that the cam surface is not long enough to maintain the .sear trigger in raised position during the entire rearward movement of the bolt, therefore an auxiliary shield 44 to form a continuation of said cam surface 42 is provided. Such a shield however may be dispensed with by providing a bolt having a longer camto support the sear,

trigger at all retracted positions of the bolt. The trigger motor is further provided with means whereby stray or accidental with the top face of the sear when the magnet is deenergized. If, however, for any reason the holding magnet is not energized at the time the bolt is returning to firing position, the sear trigger will not be retained in raised position by the electromagnet, but will be forced by the spring 25 to follow the declining face of cam 42 as the bolt resumes firing position, with the result that the block 45 of the sear trigger will engage the side face of the sear, and be moved laterally thereby, as shown in Figs. 10 and 11, without releasing said sear. It, therefore, will be seen that the piece will not be fired unless the holding magnet is energized at the moment the bolt resumes its firing position, and if the control system should be accidentally put out of action by the fire from the gun of a hostile machine, or any other cause, the automatic action of the gun will immediately be stopped.

As a further means of safety, means con trolled at the will of the operator are provided to render the sear trigger inoperative comprising a pivoted cam 47 adapted to engage the extreme end of the armature 24, and to hold the sear trigger in safe position out of engagement with the sear. ,lVhen desired, said cam 47 may be operated by the lever 48, extending through the housing 36 of the trigger motor.

Any desired arrangement may be used for the purpose of having the bolt or other part of the gun mechanism close a contact of the gun switch 29 only when the gun is ready to fire, thus a cam surface 49 on the bolt 48 can be utilized to press a spring contact 50 in the casing wall to closing position, when the bolt is in firing position, the spring of the contact forcing the same to open the circuit When the bolt is retracted. In this matter also this invention is not limited to the particular form of contact means em ployed.

The cycle of operation in starting the gun is as follows: The circuit through the primary induction winding and holding magnet being closed and a cartridge belt inserted in the feed channel of the gun, the breech bolt is moved by hand to the rear and permitted to return under spring pressure to firing position. By this motion the first cartridge is withdrawn from the feed belt and placed in firing position, the backward motion of the bolt also cocking the firing pin, setting the sear and setting the sear trlgger to cocked position. The release magnet being energized, holds the sear trigger in cocked position ready to-operate the sear, and the bolt, on resuming the firing position, closes the secondary circuit at the safety switch. lVhen ready to fire, the hand switch or mouth switch, as the case may be, is closed, and at the instant when the circuit is closed at the timing mechanism or control contact operated by the propeller, the gun is fired. The firing of the gun causes the bolt to recoil and in this manner eject the expended cartridge, supply a new cartridge to the gun, and cook the firing pin and sear trigger. During the recoil of the bolt the safety switch is open, and the secondary circuit is inoperative at that point until the bolt again resumes the firing po sition.

Normal voltage passing through the primary induction Winding and the holding magnet, is' sufficient to hold the armature down and the sear trigger cocked. At the instant that the circuit through the secondary induction winding is closed by the successive series contacts at the timing motor, hand trigger and safety switch, a voltage greatly in excess of that in the primary winding is introduced in the opposite directionin the primary winding. This is due to the much smaller number of turns in the secondary. This increased voltage in opposition to that in the circuit causes a denergization of the holding magnet. When the secondary circuit is opened at any one of the contacts, a voltage greatly in excess of that normally in the primary or main circuit is quickly introduced in the direction of the voltage in the primary and again causes the magnet to be energized. Though the period between the deenergization and renergization of the magnet may be of short duration it is sufficient to permit the sear trigger spring to exert its full effect and cause the gun to be fired before the holding magnet is again energized to attract its armature and again places the sear trigger in proper position to engage the sear and hold it when the bolt again resumes the firing position. I

In case there is any failure of the electrical system, the holding magnet will not maintain the sear trigger in raised and operative position over the sear, but the sear trigger will engage the side of the sear in inoperative position, and the gun will imance is omitted and the controlling switches are placed in the main circuit in parallel with one another, except where two or more volition switches are used they are placed in series. It will be observed that the safety switch 51, propeller switch 52, and volition switch 53, 53 form three separate return paths for the current and each must be interrupted in order to have the magnet deenergized and fire the gun. The contacts therefore are open, rather than closed in the operating condition. In other respects this arrangement is substantially the same as that first described.

With both arrangements in case the recoil or safety switch comes to the firing position,

while the propeller switch is in the firing position, the holding magnet may or may not be denergized sufficiently to release the sear trigger, assuming that all switches are in the firing position at that instant. This is of no consequence in the arrangement shown in Fig. 1, since the holding magnet is suddenly reenergized as the propeller blades pass the firing position. The magnetic energy for this purpose comes from the inductance caused by opening the secondary circuit, as above explained.

In the form shown in Fig. 2 there is no sudden reenergization of the holdingmagnet and as a result if it is only partly deenergized when the propeller blades are in the firing position, a mechanical vibrationmay cause the release of the sear trigger, after the propeller blades have passed the firing position. This would cause a stray shot. While the probabilities of stray shots are very small, yet the form shown in Fig. 1 is preferred over that shown in Fig. 2 as it does not have this possibility of stray shots.

The second arrangement by which the gun is fired by opening the circuit through the holding magnet is shown in Figs. 3, and 14.

Here there is only one switch '54 in the main circuit and this is operated by a cam 55 on the propeller or other rotating part of the motor. The arrangement is such, however, that this switch can be opened by the cam only when the gun is fully loaded, ready to fire, and the operator desires the gun to fire.

The circuit between the levers 56and 57 is broken when the propeller is in the firing position by the lower surface of the cam 55 then permitting the contacts to .separate, provided the relay magnet 58 is energized. If the magnet is not energized the armature 59 will not be attracted and consequently lever 57 abuts the end of the armature before lever 56 reaches stop 60. The circuit of the relay magnet is controlled by the gun switch 51 and the volition switch 53 in series, that is, both switches must be closed in order to have the magnet energized. It is obvious that one or more volition switches in parallel can be employed.

It is further noted that because of the hooked end of lever 57 this member and the armature 59 of the relay engage in such a way that the relay cannot operate while the cam is in the firing position, therefore the gun fires only in case the gun switch is closed before the cam reaches the firing position. The condenser 61 and non-inductive resistance 62, in parallel with the electromagnet 58 of the relay circuit, are for the purpose of preventing sparking at the contacts.

The arrangement shown in Fig. 14 can be made of less weight than the form shown in Fig. 12 and has the further advantage that it can be fired only at a definite point in the rotation of the propeller.

In the form Fig. 12, the gun'may be fired at any time during the period in which the circuit is closed at the propeller contact, which extends through an appreciable arc.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

1. A device for timing the firing of automatic airplane firearms in phase with the rotation of the propeller of the airplanes,

comprising an electric circuit, a normally energized magnet in the circuit maintaining the firing mechanism in cocked position, and

means conjointly controlled by the firearm and a part moving in phase with the propeller to deenergize the magnet.

2. Synchronizing apparatus for automatic airplane firearms comprising firing mechanism for the firearm, a part moving in phase with the propeller, an electric circuit, a normally energized magnet in the circuit to maintain the fining mechanism in cocked condition, and means conjointly controlled by the moving art and the firing mechanism to deenergize the magnet.

3. The combination with an automatic firearm of a control system comprising means operable by the moving parts of said firearm tostore suflicient mechanical energy for releasing the sear, and electrically operated means to control said sear-releasing means. 4

4. The combination wi h an automatic firearm of a control system comprising means operable by the moving parts of said firearm to store suificient mechanical energy for releasing the sear, and electrically operated means to retain or release said energy storing means.

5. The combination with an automatic firearm of a control system comprisin means operable by the'moving parts of sai firearm to store suflicient mechanical energy for releasing the sear, and means controlled in part by said fire-arm for controlling said sear releasing means, comprising an electromagnet, an electrical circuit, and means to deener ize said electro-magnet.

6. T e vcombination with an automatic firearm of a control system comprising a movable member normally adapted to opera-te the'sear of the gun while said sear is in the cocked position, means associated with the moving parts of said gun for moving said member into operative position, an electric circuit, an electro-magnet for retaining said member in operative position and means to de'einergize said electro-magnet.

7. The combination with an automatic firearm, of a control system comprising tension means to operate the firing means while said firing means is in the cocked position, means associated with the moving parts of the gun for moving said tension means into operative position, an electric circuit, an electro-magnet for retaining said tension means in operative position, and means to de'e nergize said magnet.

8. In an electric control system for automatic firearms, a primary circuit including an electro-magnet and an induction coil; and a secondary circuit having substantially less resistance than said primary circuit and having inductive relation with said primary induction coil, and means to control the flow of current in said secondary circuit, said means being controlled in partlby the firearm.

9. In an electric control system for automatic firearms, a primary circuit including a normally energized electro-magnet to maintain the firing mechanism of the gun in cocked position, and an induction coil; and

a secondary circuit having a secondary coil in inductive relation with said primary coil, and a plurality of control switches in said secondary circuit, one of said control switches being operable by the fire-arm.

10. In an. electric control system for automatic firearms, a normally closed primary circuit including an electro-magnet to control the firing mechanism of a gun and a primary coil, and a secondary circuit including a coil in inductive relation with said matic airplane firearms, a primary circuitincluding a normally energized electro-magnet to control the firing mechanism of a gun and an inductive coil; and a secondary circuit adapted to introduce a counter E. M. F. in said primary induction coil and means conjointly controlledby the fire-arm and a part moving in phase with the propeller to' make and break said secondary circuit.

12. In an electric control system for automatic airplane firearms, a primary circuitincluding a normally energized electro-magnet to control the firing mechanlsm of a gun and an induction c011; and a secondarycir- 'cuit having inductive relation with said primary induction coil and means conjointly controlled by the fire-arm and a part moving in phase with the propeller to make and break said secondary circuit.

13. In an electric control system for automatic airplane firearms, a primary circuit including a normally energized electro-magnet to control the firing mechanism of a gun and an induction winding; and a secondar circuit adapted to introduce a counter E. F. in said induction winding and having a plurality of control switches-which must be conjointly operated by the fire-arm and a part moving in phase with the propeller, to close said secondary circuit. Y

14. In an electric control system for automatic firearms, a primary circuit through a normally energized electro-magnet to control the firing mechanisrrf of a gun and one winding of an induction coil, a condenser in parallel with said electro-magnet, and a secondary circuit including a secondary winding in said induction coil, and means controlled in part by the fire-arm' for controlling the current in said secondary circuit.

15. In an electric control system for automatic airplane firearms, a primary circuit including an electro-magnet to maintain the mechanism of the gun in cocked position, and a secondary circuit in inductive relation with said primary circuit, said secondary circuit having a plurality of positively operated control switches in series, one of the said switches operating in phase with the propeller, and another of said switches operating in phase with the mechanism of the gun.

16. In an electric control system for automatic airplane firearms, a primary circuit including an electro-magnet to maintain the mechanism of the gun in cocked osition, and a secondary circuit in inductive relation with said primary circuit, said secondary circuit having a plurality of control switches conjointly controlled by the firearm and a part moving in phase with the propeller in series and a plurality of volition switches in pa 'allcl with each other and in series with said conjointly controlled switches.

17. The combination with an automatic firearm of a control system comprising an arm to operate the sear while said sear is,

in the cocked position, means associated with the moving parts of the gun for moving said arm into operative position with the sear, an electric circuit, an armature integral with said arm. an electro-magnet adapted to retain or release said armature, and means to control -the electric current in said electro-magnet.

18. The combination with an automatic firearm of a control system comprising an arm adapted to engage the sear, a spring under normal tension and co-acting with said arm and having sufficient tension to release the sear, means associated with the moving parts of the gun for moving said arm into operative relation with the sear, an electro-magnet to retain said arm in operative relation with the sear, and means to deenergize the electro-magnet.

19. Synchronizing apparatus for automatic airplane firearms, comprising an arm under normal tension adapted to operate the firing means while in cocked position, means associated with the moving parts of the gun for moving said arm into operative position, an electro-magnet for retaining said arm in operative position, and means conjointly operated by a part moving in phase with the" propeller and the moving parts of the gun for energizing and denergizing said electro-magnet.

20. A control system for automatic firearms, comprising an arm under normal tension. adapted to operate the firing means while said firing means is in the cocked position, a bolt, a cam on said bolt to move said arm into operative position, an electro-magnet for retaining said arm in operative position, and means to denergize the electromagnet.

21. In combination with an electrically controlled trigger, of a supplemental portion thereof to operate the sear, and means for displacing said portion and rendering the trigger inoperative upon failure of the electrical controlling means.

FRANK VVENNER. FRED J MAR-TEL. 

